FRIDAY, Aug. 30, 2019 (HealthDay News) -- Many Americans who die waiting for a kidney transplant actually had donor organs offered to them multiple times -- but their transplant center declined them.

That's the finding of a new study of over 280,000 U.S. patients who were on kidney transplant waitlists between 2008 and 2015.

It may come as a surprise to anyone who's assumed that when patients languish on waitlists, it's because no donor organ is available. But, in reality, of patients in this study, those who ultimately died had been offered anywhere from six to 41 donor kidneys.

"This isn't something that's widely known, even in the transplant community," said senior researcher Dr. Sumit Mohan, an associate professor of medicine at Columbia University, in New York City.

In fact, patients are often kept in the dark -- never knowing that a kidney, or multiple ones, were offered but declined.

"They aren't told, even after the fact," Mohan said.

Why would transplant centers routinely decline kidneys? In almost 93% of cases, the study found, they cite concerns about the "quality" of the organ or the deceased donor.

But when offer after offer is being rejected, that doesn't add up, Mohan said. Plus, he noted, all donor kidneys in this study were eventually transplanted into someone -- which means they clearly were acceptable.

Instead, Mohan said, it seems transplant centers are being overly conservative and frequently holding out for a "better" donor kidney -- one from a younger person with no health conditions, for example.

"They're assuming that a better offer will come in soon, in the next few days or weeks," Mohan said.

But for many patients, that never happens.

The findings, published online Aug. 30 in JAMA Network Open, are based on data from the United Network for Organ Sharing. Mohan's team focused on more than 280,000 waitlist patients who received at least one offer of a donor kidney.

Overall, 9% died on the waitlist. Before their deaths, they'd received a median of 16 donor-kidney offers; that means half received more than 16.

Meanwhile, another 21% of patients were removed from the waitlist before receiving a kidney -- because of poor health, for example. They'd received a median of 15 offers.

"I think most nephrologists would be very surprised by these figures," said Dr. Joseph Vassalotti, chief medical officer for the nonprofit National Kidney Foundation. (Nephrologists are kidney disease specialists.)

But he said that while patients might find the numbers "scary," the findings are an opportunity to spread awareness -- which will ultimately be a good thing.

Vassalotti pointed to another study published earlier this week that looked at the issue of discarded donor kidneys, which never get transplanted at all.

Researchers found that over a decade, the U.S. discarded about 18% of deceased-donor kidneys it recovered -- twice the rate seen in France, a country that tends to utilize more donated organs. The United States is more likely to discard kidneys from people with conditions like high blood pressure and diabetes, which should not preclude those organs from being transplanted, according to Mohan.

The good news, Vassalotti said, is that "there's a groundswell of attention going toward these issues now."

One of the problems, Mohan's team said, is that transplant centers face pressure from Medicare to meet certain outcomes, which may push them to be too choosy in organ selection. The Centers for Medicare and Medicaid Services recently published a proposal that would change the way transplant-center performance is evaluated.

Individual centers have their own criteria for judging donor-organ quality, Mohan said. But there's no transparency about those criteria, he added, and centers generally do not inform patients that they rejected a kidney offer and explain why.

The decision to accept or decline an organ has to be made quickly -- typically within one hour, Mohan noted. But, he said, centers could still involve patients by talking with them beforehand about their preferences -- finding out if they would rather take a kidney from a donor who had high blood pressure, for instance, versus staying on dialysis.

Vassalotti agreed. He said that older patients, in particular, might be open to taking a kidney that might not function for as many years, but will get them off dialysis.

Mohan described the current situation as "paternalistic" -- and one that would not be accepted in other areas of medicine. "An oncologist wouldn't make treatment decisions on behalf of the patient," he said.